Method and apparatus for draining connecting pipes between tanks

ABSTRACT

An air and gas vessel ( 1 ) having a downward opening is mounted within a tank ( 10, 20 ) for transport of liquid, e.g., oil. From the top side of the vessel runs a conduit ( 2 ) toward the inlet of the bridging hose ( 5 ) to the next tank. The conduit ( 2 ) may be closed by means of a cock ( 3 ). When the tank is filled with liquid from level A with the cock ( 3 ) closed, a volume will be stored in the vessel ( 1 ) when the tank is filled to level B. In order to drain the bridging hose ( 5 ), the cock ( 3 ) is opened. The confined air/gas volume will use up into the bridging hose ( 5 ) and the liquid volume will run back into the tank. The tanks may then be closed by means of the cocks ( 4 ) prior to starting the transport.

The invention relates to a method and apparatus for draining fluid thatremains standing in connecting pipes, also referred to herein asbridging connections, between tanks after filling. The fluid that isfilled into the tank car s is preferably oil.

In recent years there have emerged various systems for filling the tankcars in a whole tank train with the aid of permanent connecting hosesbetween the various tank cars. The safety regulations pertaining to themovement of these types of trains requires that each individual carshall be sealed off during transport and that the bridging connectionsor hose connections shall be empty of fluid during the advancement ofthe train. Similarly, the tanks shall not be completely filled up;rather there shall remain a safety volume of air or gas which isintended to absorb the volume changes in the fluid as a result oftemperature changes

Various method have been patented and practiced, among them thatdescribed in U.S. Pat. No. 4,711,274 of Dec. 8, 1987, “External PurgeSystem for A Tank Train.” This purging method requires stored volumes ofextra blanket gas and compressed air for the operation and control ofclosure valves and an external pipe system for the entire length of thetrain.

With the proposed drainage system according to the invention, theexternal hauling of pipes and extra tanks for compressed blanket gas andcontrol air are avoided. The air or gas volume necessary for drainage iscollected and stored within the tank during the filling process. Thisenables the avoidance of equipment both on the tanks and at the terminalfor filling and emptying. When all this equipment can be eliminated,both maintenance and operation are simplified and the system thusbecomes less expensive, In addition, the air or gas volume will have aweak purge pressure corresponding to the pressure of the fluid above thecontainer. This will ensure an efficient purging of air from the storagetank and into the bridging hose that is to be drained.

The draining of the bridging hose is made possible by shutting in asufficiently large volume of air in an internal vessel within the maintank. This confinement of air or gas takes place during the filling ofthe main tank, while the liquid is rising past the lower opening of thevessel until the filing is completed. The upper part of the vessel isput into communication with the inlet to the lower portion of thebridging hose by means of a simple air conduit. The air conduit containsa cock which either closes or opens the communication between theconfined air/gas volume in the vessel and the volume in the bridginghose that is to be drained.

More specifically the invention relates to an air and gas vessel fordraining the bridging hoses between interconnected oil tanks, where oilhas remained standing in the bridging hoses after completion of thefilling process, characterized in that the vessel having a downwardturned opening is positioned in the tanks, said vessel having at theupper edge thereof a pipe with a cock connected to the bridging hosebetween the tank cars.

Further, the invention relates to a method for draining the bridginghoses between tank cars in a tank train, consisting of a downward turnedinner vessel within the tank car having a pipe and a cock connected tothe bridging hose, characterized in that prior to the filling of thetanks, the vessel is empty of liquid and the cock is closed, liquid isthen filled into the tanks from level (A) to level (B), with gas/airbeing kept confined in the vessel, the cock in the pipe is then openedto release the confined gas in the vessel up into the bridging hose inorder to displace the liquid down into the tanks at the same time as thevessel is filled with liquid from the underside.

The invention will be explained in more detail with the aid of thefigures, wherein the various parts of the invention are shown in FIG. 1,and the function is shown in FIG. 2.

FIG. 1 shows two tank cars 10, 20 connected by means of a bridging hose5. The internal vessel that may be emptied and filled with air or gas isdesignated as 1. The internal vessel 1 has its opening facing downwards.Vessel 1 has a volume corresponding to the volume of bridging hose 5,which may be, e.g., 100-200 liters. The connection 2 between vessel 1and bridging hose 5 between tanks 10 and 20 is merely a single pipe 2.This connection may be closed or opened by means of the cock 3. Cock 3may be opened and closed manually or by remote control Cocks 4 at theupper edge of tank cars 10 and 20 are used to close off the cars priorto transport. For reasons of safety this bridging hose 5 must be emptyof liquid during transport.

On FIG. 2 level A indicates that the tank is empty and the liquid levelis below the lower opening of vessel 1. Level B indicates that tank 10is full and that the liquid has flowed over into the next tank 20through overflow pipe 5. When the filling is completed, the bridginghoses 5 between the tanks will be filled, and it is this volume that isto be drained back into the tanks.

When tanks 10, 20 are empty, vessel 1 will also be empty. Before thefilling with liquid begins, the cocks 3 are to be closed. When theliquid level after the filling of the tank is at level B, there will bea volume of gas or air confined within vessel 1. This volume will beunder a certain degree of pressure depending on the height of the liquidsurface over vessel 1. To drain liquid in bridging hose 5 between thetanks, cocks 3 are opened. The confined volume of gas/air will then risethrough pipe 2 and cock 3 up into the opening of bridging hose 5. Thegas/air volume will press the liquid that remains standing in bridginghose 5 back down into the main tank simultaneously as vessel 1 will befilled with liquid from the underside that is open. If vessel 1 is ofsuch a size that the volume is greater than the volume of bridging hose5, the entire volume of bridging hose 5 will be drained down into themain tank.

What is claimed is:
 1. A drainage system for draining liquid frombridging hoses between interconnected oil tanks after completion of atank filling process wherein oil remained standing in the respectivebridging hoses, wherein each of the bridging hoses have opposite ends,each end of said opposite ends communicating with a separate oil tankcomprising, a) a container inside each tank, said container having anopen end and an opposite closed end and being positioned inside the tankwith the open end pointed in a downward direction and the closed end inan upward direction, b) a conduit in each said tank having one endconnected to the closed end of each of said containers and an oppositeend connected to one end of each of the bridging hoses, and c) a cockvalve on each said conduit between the closed end of each said containerand the one end of each of the bridging hoses, the cock valve beingprovided to open and close the conduit, wherein said cock valve, in anopen position, allows confined air within the container to enter the oneend of each of the bridging hoses through the conduit, and drain out,through the opposite end of each of the bridging hoses, the oil that hasremained standing in the bridging hoses after the completion of the tankfilling process.
 2. The system of claim 1 wherein the cock valve islocated on the conduit inside each said tank.
 3. The system of claim 1wherein a second cock valve is provided on the one end of each of saidbridging hoses outside earth said tank.
 4. The system of claim 1 whereina third cock valve is provided on the opposite end of each of saidbridging hoses outside each said tank.
 5. A method for draining bridginghoses between interconnected oil tanks, said bridging hoses being usedfor filling the interconnected oil tanks, said bridging hoses havingopposite ends, each end of said opposite ends communicating with aseparate oil tank, said method comprising, a) position an emptycontainer inside each of the tanks, said container having a closed upperend and an opposite open end, a conduit having one end connected to theclosed upper end of the container and an opposite end connected to oneend of each of the bridging hoses, a cock valve being provided on theconduit to open and close said conduit, b) close said cock valve, c)fill the tanks with liquid from level A to level B with air being keptconfined in the container, d) open the cock valve in the conduit torelease the confined air in the container up into the one end of each ofthe bridging hoses in order to displace the remained standing liquid inthe bridging hoses down into the successive tank at the same time as thecontainer is filled with liquid from the open end.